This application claims the priority of German Patent Application Serial No. 299 09 312.3, filed May 27, 1999, the subject matter of which is incorporated herein by reference.
The present invention relates to an agitator for agitating liquids in an agitator vessel, with a gas being added to the liquid, in particular for suspending solids and dispersing gas in the liquid in flue gas desulfurizing plants.
Gas injection pipes or gas injection lances have been used to date for gassing of absorbers of flue gas desulfurizing plants and formed as simple, horizontal pipes with bores or vertical pipes through which gas, normally air, is injected. These pipes or lances are, however, incapable to efficiently distribute high gas rates.
It is thus an object of the present invention to provide an improved agitator, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved agitator by which higher gas rates can be efficiently distributed in the liquid in the agitator vessel, and the injected gas can be pre-dispersed by the agitator.
These objects, and others which will become apparent hereinafter, are attained in accordance with one embodiment of the present invention by providing an agitator vessel; an agitator shaft extending into the agitator vessel, with the agitator shaft being hollow to define an interior space for conducting gas into the agitator vessel; and an agitating propeller mounted to the agitator shaft within the agitator vessel.
According to another embodiment, the agitator is provided with a hollow hub which is connected in fixed rotative engagement with the agitator shaft and through which gas is conducted for introduction into the agitator vessel.
According to still another embodiment, the agitator shaft is provided with a plurality of pipes which are securely fixed to the agitator shaft and to which gas is directly supplied from outside the agitator vessel.
Suitably, the hollow agitator shaft and the hollow hub are provided in the area of their vessel-proximal ends with transverse bores for introduction of gases into the agitator vessel.
Advantageously, a gas injection device is arranged in the area of the vessel-proximal end of the agitator shaft or the hub.
The gas injection device may be configured in the form of a plurality of pipes which extend, in particular radial, to the longitudinal axis of the agitator shaft or hub, and are in communication with the interior space of the agitator shaft or hub or the pipes connected to the agitator shaft.
According to another variation, the gas injection device is configured in the form of a chamber which surrounds the agitator shaft or the hub and is in communication with the interior space of the agitator shaft or the hub.
Preferably, the gas injection device in the form of the pipes or the chamber has outlet openings through which the gas flows into the agitator vessel and which are located on a diameter which is approximately 35 to 75% of the diameter of the agitating propeller. It is further advantageous to configure the outlet openings of the pipes and the chamber on the backside as relating to the rotation direction of the gas injection device, i.e. on the underpressure side of the pipes or the chamber. The outlet openings of the gas injection device for introducing gas into the agitator vessel are arranged, preferably, on the pressure side of the agitating propeller.
In order to prevent a recoil of gas back to the agitating propeller, the axial distance of the gas injection device to the agitating propeller is suitable approximately 25% to 75% of a diameter of the propeller.
According to another feature of the present invention, a stationary distributor head can be provided for the supply of gas.
Advantageously, the hub is configured only in the area of the inner end of the solid agitator shaft, with the gas being directly supplied to the hollow hub via a pipe which traverses the wall of the agitator vessel.